The long-term objective of this proposal is to understand how cell surface receptors and ion channels detect extracellular signals and transduce this information into physiological changes at the cellular and organismal level. This project will focus on two members of the TRP channel family that are expressed on primary afferent neurons of the pain pathway and mediate thermosensation in the mammalian peripheral nervous system. TRPV1 is an excitatory ion channel that is activated by noxious heat or capsaicin, the pungent ingredient in chili peppers. Electrophysiological and genetic studies have shown that TRPV1 contributes to the detection of noxious heat in vivo and is modulated by a variety of inflammatory agents (e.g. extracellular protons, bioactive lipids, nerve growth factor, and bradykinin), making it an essential component of the signaling pathway through which injury increases sensitivity to heat. TRPM8 is a cold-activated channel that also responds to menthol and other cooling compounds. Determining how these channels detect thermal and chemical stimuli will provide important insight into the basic molecular processes that underlie nociception and pain sensation under normal and pathological conditions. This information will also stimulate the design and development of novel analgesic agents for treating peripheral pain syndromes, such as those associated with rheumatoid arthritis, viral and diabetic neuropathies, or peri-operative wound healing. A combination of molecular genetic, biochemical, and electrophysiological methods will be used to probe the mechanisms whereby TRPV1 and TRPM8 detect and respond to chemical and physical stimuli that produce or exacerbate pain. The specific aims of the proposal are to: (i) delineate regions of TRPV1 that are required for modulation by phospholipase C and phospholipid interaction; (ii) pinpoint domains of TRPV1 that interact with TrkA, the receptor for nerve growth factor; (iii) delineate regions of TRPM8 that are required for detection of menthol and cold; (iv) determine whether and how TRPM8 is regulated by inflammatory agents or prolonged exposure to cold (i.e. adaptation).